Field of the Invention
The present invention relates to a semiconductor laser device provided, for example, for high-speed optical response use and to a method of manufacturing the semiconductor laser device.
Background Art
As a semiconductor laser device realizing high-speed optical response, distributed feedback (DFB) laser devices which are for short-distance transmission but which can be manufactured at a comparatively low cost are mainly being used. There is a demand for achieving an improvement in yield (an improvement in the number of theoretically effective chips from one wafer) of a semiconductor laser device by chip size shrinkage as well as a demand for achieving both realization of high-speed response by reducing the capacitance and an improvement in high-temperature characteristic (an improvement in heat dissipation effect) by securing an epi volume about an emission point. From the viewpoint of improving the yield, it is desirable to form a process mesa by dry etching.
In DFB laser devices used for high-speed response in the present circumstances, the resonator length, for example, is set as short as 200 microns or less in order to increase the relaxation-vibration frequency. Forming a process mesa by dry etching is indispensable to stabilization of the characteristics of a DFB laser device having a short resonator length.
Japanese Patent Laid-Open No. 2003-051636 discloses a method of manufacturing a GaN-based semiconductor laser device.
Individual semiconductor laser devices separated from each other are obtained by cleaving a group of semiconductor laser devices in a wafer state. Cleaving is breaking the substrate at boundary portions between a plurality of semiconductor laser devices called dicing streets or separating sections. There is a possibility of the substrate being broken at a portion other than the separating sections at the time of cleaving. In particular, in a case where grooves called process mesa grooves are formed on opposite sides of ridge structure, there is a problem that breakage can occur in portions reduced in thickness due to the process mesa grooves.